I need your help with my vacuum tap (and my manifold studs, too).

RustyRatRod said
The factory port in the intake is 3/8npt (national pipe thread) and is tapered. The fitting you have is a tube thread and is straight threads like a bolt. The fitting you need will have the same size hose barb as the new fitting, but will have the correct 3/8 NPT threads for the manifold. Since the threads are tapered, you do not tighten it all the way down, or you will break the manifold. They only tighten in a few threads. Make sure to seal the threads with something too.

Thanks, Rusty. Just cleaned up and installed the new tap with Teflon tape. Works and looks great. Another question for you, if you don't mind. When I install my engine block drain bolt into the side of my slant six, do I put some pipe joint compound on it to seal it against coolant leaks? Thanks - cruiser